Bio-mechanical prosthetic finger with h-shaped rocker

ABSTRACT

The disclosure provides apparatus and methods of use pertaining to a prosthetic finger assembly. In one embodiment, the assembly includes a coupling tip and a distal ring coupled with the coupling tip. The assembly further includes a proximal ring coupled with the distal ring. A rocker formed in an H-shape with a first end forming a first split prong and a second end forming a second split prong may extend between the coupling tip and the proximal ring. The coupling tip, distal ring, proximal ring, and H-shaped rocker may all be hingedly connected such that movements of the residual finger within the proximal ring articulate the distal ring together with the rocker to articulate the coupling tip. Other embodiments are also disclosed.

REFERENCE TO PENDING PRIOR PATENT APPLICATION

The application claims the benefit under 35 U.S.C. 119 (e) of U.S.Provisional Patent Application Nos. 62/111,464, filed Feb. 3, 2015 byJon Bengtsson, Robert Thompson, and Charles Colin Macduff for“BIO-MECHANICAL PROSTHETIC FINGER WITH H-SHAPED ROCKER,” and 62/209,843,filed Aug. 25, 2015 by Robert Thompson Jr., Jon Bengtsson, AnthonyCharles Peto, Sydney Tye Minnis, Eric Dennis Klumper, and Bradley ArthurCrittenden for “BIO-MECHANICAL PROSTHETIC FINGER WITH H-SHAPED ROCKER,”both of which patent applications are hereby incorporated herein byreference.

BACKGROUND

If a person loses a finger, a finger segment, or a fingertip, the resultis impaired performance of the hand. Having an amputated finger inhibitsan amputee from performing some of the most basic tasks. For example,with a lost finger or fingertip, the task of typing on a computerkeyboard or dialing on a telephone becomes significantly more difficult.These types of tasks require precise actions that only fingers are ableto offer.

Not only do they allow for the performance of precise physical actions,fingers also provide an increased ability to grip or handle items. Whileholding an item in the hand, the weight of the item is dispersed throughall of a user's fingers. By varying the force used by each finger on theholder's hand, the holder is able to manipulate the item in a myriad ofways. However, if the holder is missing all or even part of a singledigit, or if a digit is present but nonfunctioning, this freedom ofmanipulation and the number of degrees through which the holder canmanipulate the item is drastically decreased.

Current prosthetic finger solutions demonstrate several drawbacks.First, a primary category of prosthetic fingers offers only cosmeticrestoration. These prosthetics are designed to be worn passively andoffer a realistic look. They provide little to no functionality and donot enable the owner to restore functionality to his or her hand. Otherprosthetics offer the user some level of restored functionality, but arecomplex in design and electrically powered. These prosthetics, whileperhaps better than going without, are impractical in that they requirean external power source and can be both bulky and unwieldy for the userto manage. Still other prosthetic fingers are body-powered but lack thedesign flexibility necessary to accommodate any length of residualfinger (e.g., all or partially amputated and varying degrees ofamputation) while providing maximum dexterity, grip strength, and fingerarticulation.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key aspects oressential aspects of the claimed subject matter. Moreover, this Summaryis not intended for use as an aid in determining the scope of theclaimed subject matter.

One embodiment provides a biomechanically driven prosthetic fingerassembly. The biomechanically driven prosthetic finger assembly includes(1) a distal ring rotatively coupled between a coupling tip and aproximal ring via respective first and second hinged connections; and(2) a rocker rotatively coupled between the coupling tip and theproximal ring via respective third and fourth hinged connections. Thefirst and second hinged connections may define a midline relative to az-axis, where the third hinged connection is located below the midlineand the fourth hinged connection is located above the midline, such thata relative rotational motion between the proximal ring and the distalring causes a relative rotational motion between the distal ring and thecoupling tip to emulate a finger's natural closing motion.

Another embodiment provides a method of fitting a customized prostheticfinger having a proximal ring configured to anchor to a patient'sresidual finger, where the proximal ring contains one or moreshim-retainment apertures. The method begins with inserting the residualfinger into an interior of the proximal ring of the prosthetic fingerand continues with assessing a tightness of the proximal ring about theresidual finger. Next, the method includes selecting a first shim havinga first thickness from a plurality of shims configured to line theinterior of the proximal ring, each of the shims including one or moreretaining grommets, and removing the residual finger from the proximalring. Then the method involves inserting the first shim into theinterior of the proximal ring such that the retaining grommets protrudethrough the shim-retainment apertures, thereby retaining the first shimwithin the interior of the proximal ring, before reinserting theresidual finger.

The method discussed above may further include assessing a tightness ofthe first shim about the residual finger, and then removing the residualfinger and the first shim before selecting, from the plurality of shims,a second shim having a second thickness. Once the second shim isselected, the user may continue by inserting the second shim into theinterior of the proximal ring such that the retaining grommets protrudethrough the shim-retainment apertures, thereby retaining the second shimwithin the interior of the proximal ring.

Yet another embodiment provides a prosthetic finger device. Theprosthetic finger device includes (1) a distal linkage rotativelycoupled with a proximal linkage; (2) a rocker structure rotativelycoupled between a receiving tip and the proximal linkage; (3) a proximalcage ring attached to the proximal linkage; and (4) a distal cage ringattached to the distal linkage. The proximal and distal cage rings areconfigured to anchor onto a user's residual finger in a manner thatnests an end of the residual finger within the receiving tip such thatmovement of the residual finger within the proximal and distal cagerings articulates the distal and proximal linkages together with therocker to articulate the receiving tip. The proximal cage ring may beinterchangeable with a plurality of replacement proximal cage ringshaving varying diameters, and the distal cage ring may beinterchangeable with a plurality of replacement distal cage rings havingvarying diameters.

Other embodiments are also disclosed.

Additional objects, advantages and novel features of the technology willbe set forth in part in the description which follows, and in part willbecome more apparent to those skilled in the art upon examination of thefollowing, or may be learned from practice of the technology.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the present invention,including the preferred embodiment, are described with reference to thefollowing figures, wherein like reference numerals refer to like partsthroughout the various views unless otherwise specified. Illustrativeembodiments of the invention are illustrated in the drawings, in which:

FIG. 1 illustrates a perspective view of one embodiment of a prostheticfinger assembly featuring an H-shaped rocker;

FIG. 2 illustrates a left-side elevation view of the prosthetic fingerassembly of FIG. 1;

FIG. 3 illustrates an exploded view of the prosthetic finger assembly ofFIGS. 1 and 2;

FIG. 4 illustrates a top view of the prosthetic finger assembly of FIGS.1-3, with a centerline axis bisecting the assembly relative to a y-axis;

FIG. 5 illustrates another left-side view of the prosthetic fingerassembly of FIGS. 1-4, with a midline axis intersecting first and secondhinged connections relative to a z-axis;

FIG. 6 illustrates an end view of the prosthetic finger assembly ofFIGS. 1-5 with an inserted shim;

FIG. 7 illustrates a flow chart depicting an exemplary method of fittingthe prosthetic finger assembly of FIGS. 1-6;

FIG. 8 illustrates a perspective view of one embodiment of a prostheticfinger device having a single rocker connecting a cupped receiving tipwith a distal linkage and a proximal linkage;

FIG. 9 illustrates a top view of the prosthetic finger device of FIG. 6;

FIG. 10 illustrates a bottom view of the prosthetic finger device ofFIGS. 8-9; and

FIG. 11 illustrates another perspective view of the prosthetic fingerdevice of FIGS. 8-10 with the cupped receiving tip in an extendedposition.

DETAILED DESCRIPTION

Embodiments are described more fully below in sufficient detail toenable those skilled in the art to practice the system and method.However, embodiments may be implemented in many different forms andshould not be construed as being limited to the embodiments set forthherein. The following detailed description is, therefore, not to betaken in a limiting sense.

Various embodiments disclosed herein relate to a custom-designed,self-contained prosthetic finger that can be fitted for a user with anamputated finger, fingertip, or finger segment. The streamlined,sophisticated, and biomechanically driven design allows for a patientwith any level of residual finger to utilize a mechanical replacementthat mimics the motions and functionalities of a real finger. Thenatural action of the prosthetic finger assembly allows users to regainmaximum control of the flexion and extension movements of a full fingerand fingertip and is designed to bend and curl in a realistic, naturalmanner in response to movement in the user's residual finger or adjacentfingers.

Embodiments described herein feature specially designed components, suchas an H-shaped rocker and/or a cupped receiving tip, both discussed indetail below, that allow the prosthetic finger to anchor to any lengthof residual finger, while protecting the amputation site against furtherinjury or hypersensitivity and providing the individual user withmaximum fit and use flexibility, dexterity, grip strength, andarticulation. As a result, the prosthetic finger offers digit amputees afunctional solution that eases the transition back into dailyactivities, no matter how intricate, after amputation.

FIGS. 1-3 illustrate perspective, side, and exploded views of oneembodiment of a prosthetic finger 100. In this embodiment, prostheticfinger 100 may include four major interconnected components that extendfrom a proximal end located at the patient's hand to a distal endlocated at a distance from the patient's hand. These components includea proximal ring 102, a distal ring 104, a coupling tip 106, and anH-shaped rocker 108. Proximal ring 102 and distal ring 104 may each havea respective body 112, 113. In this embodiment, bodies 112, 113 may formcircular or ring shapes that are configured to anchor onto apatient's/user's residual finger. More specifically, body 112 ofproximal ring 102 may be configured to anchor about a proximal phalanxof a user's residual finger with a snug fit. Similarly, body 113 ofdistal ring 104 may be configured to anchor about a middle phalanx of auser's residual finger with a snug fit.

A series of hinges may be used to secure the four primary componentsdiscussed above via rotative connections. In one embodiment, theserotative connections may be particularly positioned with respect to apair of axes detailed in FIGS. 4-5. More specifically, FIG. 4 depicts acenterline, C, that bisects prosthetic finger 100 relative to a y-axis,and FIG. 5 shows a midline, M, that intersects a first hinged connection110 and a second hinged connection 114, both detailed below, relative toa z-axis.

Turning to the various rotative connections shown in FIGS. 1-2, distalring 104 may rotatively couple with coupling tip 106 via first hingedconnection 110. First hinged connection 110 may include a pair ofparallel pivotal hinges that are symmetric about centerline, C,discussed above in relation to FIG. 4. Each of the pivotal hinges ofconnection 110 may provide a pivot point between distal ring 104 andcoupling tip 106.

Proximal ring 102 may rotatively couple with distal ring 104 via secondhinged connection 114. Second hinged connection 114 may also include apair of parallel pivotal hinges that are symmetric about the centerline,C, one located on each side of prosthetic finger 100 such that eachprovides a pivot point between proximal ring 102 and distal ring 104. Asdiscussed above in relation to FIG. 5, the midline, M, intersects hingedconnections 110 and 114, and, therefore, both first and second hingedconnections 110, 114 are located directly upon the midline, M, relativeto the z-axis.

Rocker 108 may form a H-shape having opposing first and second ends 116,118, respectively, that extend between coupling tip 106 and proximalring 102. First end 116 may form a first split prong of the H-shape androtatively couple with coupling tip 106 via a third hinged connection120 (FIGS. 1-2) located below the midline, M, relative to the z-axis.Second end 118 may form a second split prong of the H-shape androtatively couple with proximal ring 102 via a fourth hinged connection122 (FIGS. 1-2) located above the midline, M, relative to the z-axis.Both third and fourth hinged connections 120, 122 may include a pair ofparallel pivotal hinges that are symmetric about the centerline, C, eachproviding a pivot point between rocker 108 and coupling tip 106/proximalring 102.

Any one or more of the first, second, third, and/or fourth hingedconnections 110, 114, 120, 122 may be outfitted with hard-stops toprevent hyperextension of finger 100 during operation. For example, ahard-stop 127, shown in FIG. 1, may prevent relative over-rotation offirst hinged connection 110, or between distal ring 104 and coupling tip106. Mechanical hard-stops may have any appropriate size, shape, and/orconfiguration.

Working together, proximal ring 102, distal ring 104, coupling tip 106,and H-shaped rocker 108 form a 4-bar linkage system that allows thecoupling tip to be articulated in response to a pulling force on distalring 104, which places the member in tension and reduces the risk ofbuckling. Thus, natural movement of the patient's residual finger seatedwithin proximal ring 102 and distal ring 104, or in some cases movementof his or her adjacent fingers, may be used to actuate realistic flexionand extension motions within prosthetic finger 100. Users may performtheir full range of usual activities, including typing, playing amusical instrument, or any other activity that requires the fulldexterity of the hand.

The H-shape of rocker 108 allows third hinged connection 120 betweenrocker 108 and coupling tip 106 to occur outside the assembly, oroutside the physical boundary defined by distal ring 104 and couplingtip 106. This configuration allows users with a relatively longerresidual finger, or a relatively long middle phalanx, to take advantageof additional clearance space within the assembly. The residual fingermay fit comfortably within the assembly, while still being protectedagainst further damage and/or hypersensitivity. That said, while rocker108 is described herein as having an H-shaped profile, it should beunderstood that rocker 108 may take any appropriate size, shape, type,and/or configuration.

In the embodiment shown in FIGS. 1-5, coupling tip 106 may include a tippad 124. Tip pad 124 may be formed from a soft-textured silicone orother material that mimics the texture of a real finger. This aids withgripping and provides a softer touch. In one embodiment, a touchscreenmechanism (not shown) may be provided to allow the user to use theprosthetic finger to operate capacitive touchscreens, which react to thebody's natural current. The touchscreen mechanism allows the user todirect his or her own body current through the tip of the prostheticfinger.

One embodiment of coupling tip 106 may also include a nail 126, whichmimics a natural edged nail that may provide scratching and peelingfunctionalities as well as assist with fine-object manipulation.

Embodiments of prosthetic finger 100 are custom designed andindividually fitted to accommodate a variety of differing userconditions, including different residual-finger lengths (e.g., varyingamounts of loss to the finger). In this regard, each finger 100 may becustomized to fit a particular patient or user, providing both customfunctionality as well as a mechanical match to the anatomical jointarticulation of the user, including matching the length of the original,non-amputated finger. Design considerations include an amount of fingerloss, a number of joints to be replaced, and other characteristicsspecific to the individual end user. H-shaped rocker 108 is designed toprovide a full-coverage “cage” above and about a patient's residualfinger, thereby protecting the residual finger from irritation and/orhypersensitivity, without interfering with the residual finger withinthe prosthetic finger device 100. Outfitted with H-shaped rocker 108, auser may anchor any length of prosthetic finger within finger 100, evenif the residual finger length extends well past the proximalinterphalangeal (“PIP”) joint. In cases in which the user has a fullyformed, but poorly or nonfunctioning finger, coupling tip 106 may beremoved so that prosthetic finger 100 functions as a joint brace, ratherthan a digit replacement.

To further provide better aesthetics, embodiments of finger 100 may becoated with films and/or colorings matched to the user's skintone/color. An additive manufacturing process (i.e., 3D printing)facilitates this ability to customize the intricacies of the prostheticfinger design in order to optimize prosthetic finger 100 for eachpatient.

Embodiments of prosthetic finger 100 may be formed of any suitablestructural material that is non-irritating to human skin and allows theuser to operate the prosthetic with comfort and confidence. Exemplarymaterials include titanium, stainless steel, aluminum, silicone, carbonfiber, nylon, plastic/polymer, wood, rubber, gold, silver, tungsten,flex cable, neoprene, or any other suitable material. In one embodiment,components of prosthetic finger 100 are 3D printed from Duraform EXpolymer material.

Using biocompatible materials, various embodiments of finger 100 may beapplied as an orthopedic implant that may be surgically implanted into auser's finger. This option may be applied for users having injuries thathave crushed their finger bones without the ability to heal or berepaired. In these situations, implantable embodiments of prostheticfinger 100 are able to take the place of the user's original boneswithout the need for amputation.

To use, the user may simply slide proximal ring 102 and distal ring 104onto his or her residual finger, and, if necessary, adjust further usinga shim(s). FIG. 6 depicts a rear view of prosthetic finger 100, in whichbody 112 of proximal ring 102 is outfitted with a semi-circular shim128, which may be employed to allow the sizing of body 112 to accountfor possible swelling in the fingers, weight gain/loss, or any otherpost-manufacture changes in the size of the residual finger. In furtherdetail, a fit kit (not shown) may be provided with each prostheticfinger 100 and may include a number of shims 128. In one embodiment,each shim 128 may approximate a semi-circle or U-shape configured toabut an inner diameter, d, of body 112 of proximal ring 102 and may havea number of retaining grommets 130 configured to protrude throughcorresponding shim-retainment apertures 132 within body 112. Each shim128 may have a different thickness, t, thereby allowing the user toessentially adjust the inner diameter, d, of body 112 of proximal ring102 in a number of increments as required by the user.

Once prosthetic finger 100 (adjusted or otherwise) is in place, the usercan utilize his or her natural movements of the residual finger. Theprimary components of prosthetic finger 100 will articulate using thesame cognitive process that was previously utilized for the originalfinger. If a user wears multiple fingers 100, each may be individuallyoperated.

FIG. 7 provides a flow chart depicting an exemplary method 150 forinstalling and adjusting, or fitting, one embodiment of prostheticfinger 100 upon a user's residual finger. The method begins withinserting (152) the residual finger into body 112 of proximal ring 102and assessing a tightness (154) of body 112 about the residual finger.Depending on this assessment (154), the user, a medical professional, oranother assistant may select a first shim 128 (156) from the fit kit oranother source. The user may then remove the residual finger (158) fromproximal ring 102 and insert first shim 128 (160) into the innerdiameter, d, of body 112 such that first shim 128 lines the innerdiameter, d, while retaining grommets 130 protrude throughshim-retainment apertures 132. Once first shim is installed (160), theuser may reinsert the residual finger (162) into proximal ring 102 andassess a tightness (164) of first shim 128 (which now lines body 112 ofproximal ring 102) about the residual finger. If the shimmed proximalring 102 fits, method 150 is complete (166), and the user may proceed tobiomechanically drive prosthetic finger 100. If shimmed proximal ring102 does not fit, method 150 may return to the step of selecting a shim(156), in which a second shim having a different thickness may beselected before proceeding. The user may experiment with multiple shimsof varying thicknesses until an ideal or desired fit is achieved. Ofcourse, distal ring 104 may be adjusted in a manner similar to thatdiscussed with respect to proximal ring 102 and method 150.

FIGS. 8-11 illustrate first perspective, top, bottom, and secondperspective views of an alternate embodiment of a prosthetic finger 200.In this embodiment, prosthetic finger 200 includes three primaryinterlinked components: a rocker 202 having a proximal end 204 and adistal end 206, a proximal linkage 208, and a distal linkage 210. Infurther detail, and as shown in FIGS. 8-9, distal linkage 210 mayrotatively couple with proximal linkage 208, which may, in turn, couplewith proximal end 204 of rocker 202. Distal end 206 of rocker 202 mayrotatively couple with a swiveling tip brace 211. Swiveling tip brace211 may feature a tip fastener joint 226, shown in FIGS. 8-9 and 11,that allows a receiving tip 212 to be positioned at varying anglesrelative to swiveling tip brace 211 and to the remainder of prostheticfinger 200 in order to achieve different grip strengths and/orarticulation characteristics. A tip pad 214 may attach to tip 212 in anyappropriate manner.

Two cage rings may attach to the linkages for the purpose of retaining auser's residual finger (with one ring proximal of the proximalinterphalangeal (“PIP”) joint and another ring distal of the PIP joint)and translating movement of the residual finger through the interlinkedassembly discussed above. As shown in FIGS. 6-9, a proximal cage ring216 and a distal cage ring 218 may attach to proximal linkage 208 anddistal linkage 210, respectively. This attachment may be facilitated bya universal ring mount 220 located on each of proximal linkage 208 anddistal linkage 210. Each universal ring mount 220 may define a ringmount aperture 224 that is configured to receive an attachmentprotrusion 222 of each of cage rings 216, 218.

In use, a user/patient may slide proximal and distal cage rings 216, 218of prosthetic finger 200 over his or her residual finger like a ring.Each finger 200 may be customized to fit the particular user inquestion. As a result, rocker 202, proximal and distal linkages 208,210, and/or swiveling tip brace 211 may be customized to accommodate thelength of the user's residual finger or other physical characteristic ofthe particular user, such that when prosthetic finger 200 is anchored tothe user's residual finger, an end or tip of the residual finger maynest within or adjacent to receiving tip 212. In one embodiment,receiving tip 212 may be curved or “cupped” to receive the residualfinger end or tip in a manner that protects the user's finger fromfurther damage and/or hypersensitivity. The components of prostheticfinger 200 not only look realistic during articulation, but receivingtip 212, with a residual finger end or tip nested therein, bends in arealistic manner as rocker 202 is articulated.

While prosthetic finger 200 may be custom designed to custom fit eachuser, post-manufacturing changes to the patient's physiology may occur.To add post-manufacturing customization capabilities to prostheticfinger 200, both proximal cage ring 216 and distal cage ring 218 may beinterchangeable such that they may be swapped out with rings of varyingsizes to address sizing and/or swelling fluctuations demonstrated in theresidual finger of the patient. Varying sizes of proximal and distalcage rings 216, 218 may be provided in a fit kit (not shown), allowingthe user to employ the most appropriate ring sizes in real-time. Theuser may easily interchange cage rings by removing the rings 216, 218from, and replacing different rings to, ring mounts 220 via ring mountapertures 224 and attachment protrusions 222. Interchangeable rings 216,218 may be formed of any appropriate material including flexiblepolymers or other plastics that are non-irritating to human skin.

Embodiments of the prosthetic fingers 100, 200 described above exhibitnumerous unique characteristics and provide a variety of medicalbenefits. An individual's unique physiology and lifestyle patternsdictate the function and performance expected of his or her hands. Usingembodiments of the prosthetic fingers described herein, patients mayregain independent control of their hands, whether at work or at play.Each device is custom designed, manufactured for a specific individual,and incorporates features that allow for further fine-tuning andadjustment of fit to account for post-manufacturing fluctuations (e.g.,shims and or interchangeable rings), enabling the device to fit the userin a manner that allows for a biomechanically driven, low profile,lightweight, highly functioning return to the user's everydayactivities, no matter what those activities might entail. A few examplesinclude typing, playing the piano or another instrument, woodworking,and much more.

Embodiments of the prosthetic fingers described above are body powered,and their linked components articulate when the user simply moves his orher residual finger, when available, or an adjacent finger whennecessary. Beyond allowing for a simple, elegant, and streamlined designthat offers strength in the lowest possible profile design, employingthe user's own biomechanics to drive embodiments of prosthetic fingers100, 200 provides a host of medical benefits to the user, includingreduced swelling of and increased circulation to the residual finger andthe hand as a whole, supporting healthy joints in the injured andadjacent fingers.

Although the above embodiments have been described in language that isspecific to certain structures, elements, compositions, andmethodological steps, it is to be understood that the technology definedin the appended claims is not necessarily limited to the specificstructures, elements, compositions and/or steps described. Rather, thespecific aspects and steps are described as forms of implementing theclaimed technology. Since many embodiments of the technology can bepracticed without departing from the spirit and scope of the invention,the invention resides in the claims hereinafter appended.

1. (canceled)
 2. A biomechanically driven prosthetic finger assembly,comprising: a distal ring rotatively coupled between a coupling tip anda proximal ring via respective first and second hinged connections; anda rocker rotatively coupled between the coupling tip and the proximalring via respective third and fourth hinged connections, wherein: thefirst and second hinged connections define a midline relative to az-axis: the third hinged connection is located below the midline; thefourth hinged connection is located above the midline, such that arelative rotational motion between the proximal ring and the distal ringcauses a relative rotational motion between the distal ring and thecoupling tip to emulate a finger's natural closing motion; and whereinthe rocker defines an H-shape having opposing first and second ends, thefirst end forming a first split prong at the third hinged connection,and the second end forming a second split prong at the fourth hingedconnection.
 3. The prosthetic finger assembly of claim 2, wherein eachof the first, second, third, and fourth hinged connections comprises apair of parallel pivotal hinges that are symmetric about a centerlinethat bisects the prosthetic finger assembly relative to a y-axis.
 4. Theprosthetic finger assembly of claim 2, wherein the distal ring isconfigured to anchor about a middle phalanx of a residual finger with asnug fit.
 5. The prosthetic finger assembly of claim 2, wherein theproximal ring is configured to anchor about a proximal phalanx of theresidual finger with a snug fit.
 6. (canceled)
 7. The prosthetic fingerassembly of claim 2, wherein the coupling tip includes a tip pad.
 8. Theprosthetic finger assembly of claim 2, further comprising a plurality ofinterchangeable sizing shims, each of the sizing shims configured toline one or both of the proximal and distal rings.
 9. The prostheticfinger assembly of claim 8, wherein at least one of the proximal ringand the distal ring comprises a shim-retainment aperture configured toreceive and retain one of the sizing shims.
 10. The prosthetic fingerassembly of claim 2, wherein one or more of the coupling tip, the distalring, the proximal ring, and the rocker are 3D printed from anengineering-grade polymer. 11-20. (canceled)
 21. A prosthetic fingerdevice, comprising: a distal ring rotatively coupled between a couplingtip and a proximal ring via respective first and second hingedconnections; a rocker rotatively coupled between the coupling tip andthe proximal ring via respective third and fourth hinged connections,wherein the rocker defines opposing first and second ends, the first endforming a first split prong at the third hinged connection, and thesecond end forming a second split prong at the fourth hinged connection;and a plurality of interchangeable sizing shims, each of the sizingshims configured to line one or both of the proximal and the distalrings.
 22. The prosthetic finger device of claim 21, wherein at leastone of the proximal ring and the distal ring comprises a shim-retainmentaperture configured to receive and retain one of the sizing shims.